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UNIVERSITY  OF  ILLINOIS, 

Agricultural  Experiment  Station. 

CHAMPAIGN,  AUGUST,  1889. 


BULLETIN  NO.  6. 


A  BACTERIAL  DISEASE  OF  CORN. 


INTRODUCTORY. 

Maize,  or  Indian  corn,  is  the  most  important  crop  throughout  a  very 
large  portion  of  the  United  States,  and  so  any  injury  whatever  to  the  plant 
is  a  matter  of  serious  concern.  In  the  whole  range  of  the  vegetable  king- 
dom there  are  few  plants  that  can  compare  with  it  in  normal  vigor  and 
abundant  general  productiveness.  No  other  agricultural  crop  so  domi- 
nates the  appearance  of  the  fields  throughout  the  great  corn  belt  in  our 
country,  and  none  returns  to  the  pockets  of  the  producers  so  large  a  total 
sum  of  cash.  "Corn  is  king,"  and  apparently  must  remain  so  in  the 
political  economy  of  our  part  of  the  world. 

To  those  who  have  made  themselves  acquainted  with  the  prevalent 
diseases  and  injuries  of  other  vegetable  productions  and  who  reflect  upon 
the  vast  areas  annually  planted  to  corn,  often  successively  during  many 
years  on  the  same  land,  it  must  be  a  matter  of  supreme  satisfaction  that 
this  magnificient  staple  so  far,  to  an  exceptionable  degree,  escapes  the 
harmful  attacks  of  vegetable  and  animal  parasites  and  the  destructive  rav- 
ages of  larger  insect  and  other  animals.  Still,  because  of  the  immense 
amount  of  the  cereal  produced,  the  total  annual  losses  from  such  causes 
make  a  vast  financial  showing.  The  entomologists  count  insect  pests 
injurious  to  corn  by  the  score,  some  of  which  are  charged  with  enormous 
aggregate  destruction.  No  one  has  more  carefully  studied  or  more  fully 
made  known  these  insect  depredators  than  Professor  S.  A.  Forbes,  State 
Entomologist  of  Illinois,  as  his  published  reports  show.  In  a  lecture  on 
"  Insects  Affecting  Corn,"  delivered  by  him  before  many  farmers'  institutes 
in  Illinois,  during  the  last  half-dozen  years,  he  has  brought  together  and 


1 66  BULLETIN    NO.    6.  [August, 

presented  in  a  popular  manner  the  existing  information  upon  the  subject, 
with  enlarged  illustrations  of  several  species  and  representations  of  their 
work. 

Besides  the  destruction  by  insects,  there  is  known  to  be  considerable 
loss  from  fungous  parasites.  Among  these  the  best  known  is  "smut," — 
the  great  sooty  masses  that  form  on  any  part  of  the  plant  above  ground, 
but  very  commonly  on  the  ear,  which  the  fungus  more  or  less  displaces 
by  its  own  unsightly  production.  This  smut  is  a  vegetable  parasite.  It 
sends  its  delicate  fibres — much  too  fine  to  be  seen  with  the  unaided  eye — 
through  and  through  the  tissues  of  the  stalk,  beginning  when  the  latter  is 
is  very  young,  and  finally  forms  its  abundant  mass  of  black  spores  in  the 
swollen  projections  so  well  recognized  by  every  one.  These  sooty  spores 
are  the  germs  for  the  next  year's  smut,  enough  of  them  lasting  over  winter 
to  perpetuate  the  fungus.  There  is  also  a  rust  upon  the  leaves  of  corn 
quite  similar  to  that  known  by  the  same  name  on  wheat,  but  compara- 
tively much  less  destructive.  This,  too,  is  a  fungus,  growing  in  the  tissues 
and  living  upon  the  juices  of  the  corn  plant.  A  few  others  of  somewhat 
like  character  are  known  to  injure  the  crop,  especially  during  certain  sea- 
sons unusually  favorable  to  their  development. 

But  we  are  to  write  of  quite  another  thing.  We  hear  much  nowadays 
of  "disease  germs."  It  has  been  positively  ascertained,  and  is  now  gen- 
erally accepted  as  an  incontrovertible  fact,  that  the  communicable  dis- 
eases of  animals  (including  man),  that  is,  those  which  are  transmissible 
from  diseased  to  healthy  individuals,  are  dus  to  living  organisms.  These 
gain  entrance  in  some  way  to  the  body,  rapidly  multiply  in  number,  take 
their  nourishment  from  the  normal  stores  of  the  animal,  and  usually  cause 
therein  injurious  chemical  changes.  By  far  the  largest  number  of  these 
disease  agents  belongs  to  the  group  of  exceedingly  minute  plants  called 
bacteria — a  word  with  which  all  are  now  familiar,  though  those  who  have 
not  had  the  opportunity  of  seeing  them  under  a  compound  microscope  of 
high  power  may  not  have  a  very  definite  idea  of  the  organisms  themselves. 
An  individual  among  them  consists  of  a  single  cell,  which  owing  to  its 
exceedingly  minute  size  can  not  be  very  well  studied  as  to  its  further 
structure.  It  is,  however,  known  to  consist  of  an  outer  membrane  or 
wall  with  contents  of  a  different  character.  There  are  no  organs  or  mem- 
bers of  any  kind,  save  that  some  varieties  have  issuing  from  one  or  both 
ends  of  the  miniature  body  a  hair-like  projection  capable  of  rapid  vibra- 
tory motion  by  which  the  little  individual  swims  in  the  liquid  in  which  it 
is  immersed.  Food  can  be  taken  only  in  the  liquid  state,  by  absorption 
through  the  exterior  wall.  Multiplication  takes  place  by  a  single 
cell  becoming  transversely  divided  and  the  two  parts  enlarging  so  as  to 
form  two  cells,  each  of  which  is  exactly  like  the  original  one.  In  all  cases 
the  two  young  cells  may  at  once  separate,  but  in  the  case  of  certain  spe- 
cies they  commonly  remain  attached  so  as  to  form  a  necklace-like  string, 
or,  with  certain  others,  in  little  squares  with  the  individuals  in  rows  both 
ways.  Some  kinds  produce  "spores."  The  contents  of  a  cell  collect  in 


1889]  A    BACTERIAL    DISEASE    OF    CORN.  167 

a  definite  manner  in  the  middle  or  at  one  end  of  the  cavity,  become  con- 
siderably condensed,  and  form  about  themselves  a  special  wall  of  their 
own.  Subsequently  the  wall  of  the  original  cell  decays  or  becomes 
dissolved,  freeing  the  internally  formed  spore.  These  spores,  owing  to 
their  greater  density  and  consequent  stronger  refraction  of  light,  have  a 
glistening  appearance  under  the  microscope.  They  are  able  to  withstand 
injurious  substances  and  degrees  of  temperature  far  beyond  that  of  the 
vegetating  cells  in  which  they  are  produced.  Under  proper  conditions 
they  may  germinate,  each  forming  again  a  cell  like  that  in  which  it  was 
formed.  This  is  the  simple  story  of  their  life.  There  is  no  sexual  or 
other  differentiation  among  the  individuals.  Any  one  may  become  two 
by  dividing,  as  described;  and,  as  this  process  can  take  place  under 
favorable  circumstances  in  a  very  short  time  and  be  constantly  repeated 
in  similar  manner,  the  number  of  individuals  increases  in  geometrical 
ratio  and  soon  becomes  enormously  great.  It  is  on  this  account  that  the 
little  things,  insignificant  as  individuals,  become  irresistible  agents  of  de- 
struction. When  disease  is  "caught"  from  one  previously  infected,  it  is 
due  to  the  transfer  of  some  of  these  living  atoms  capable  of  originating 
a  myriad  progeny  in  the  previously  healthy  body. 

Compared  with  the  number  of  communicable  diseases  due  to  bacteria 
affecting  animals,  there  are  few  known  in  the  vegetable  world,  though  some 
have  been  as  definitely  and  conclusively  established.  Among  the  latter 
may  be  counted  the  so-called  fire  blight  of  apple  and  pear  trees;  a  disease 
of  hyacinth  bulbs;  and,  without  attempting  to  exhaust  the  list,  a  disease 
of  broom- corn  and  sorghum,  *the  latter  being  very  similar  in  character- 
istics and  comparative  amount  of  injury  to  that  to  be  here  described  of 
Indian  corn. 


APPEARANCE  IN  THE  FIELD. 

The  first  indication  of  the  disease  in  a  field  of  corn  as  noticed  in 
ordinary  observation,  is  the  dwarfed  condition  of  the  young  plants.  This 
commonly  occurs  in  spots  of  various  sizes  from  a  few  square  rods  to  an  acre 
or  more,  and  often,  though  by  no  means  always,  on  soil  of  character  some- 
what different  from  the  rest  of  the  field.  It  seems  hard  to  designate  what 
special  condition  or  quality  of  soil  is  most  usually  associated  with  the 
disease;  but,  upon  the  whole,  it  is  found  in  the  rich  spots  rather  than  in 
those  of  poorer  quality.  In  many  cases  it  is  upon  the  lowest  ground, 
whether  or  not  water  has  temporarily  stood  in  the  hollows.  The  most 
defin'Uely  bounded  area  noticed  was  upon  a  spot  which  had  until  the  year 
previous  been  too  wet  for  tillage  but  which  had  been  tile  drained  and  broken 
up,  the  sod  having  rotted.  This  was  planted  the  following  spring  with  the 
rest  of  the  field  and  no  part  seemed  to  be  in  better  condition  for  a  heavy 


*  Kurrill :  Proceedings  American  Society  of  Microscopists,  1887. 

"          Proceedings  Society  for  the  Promotion  of  Agricultural  Science,  1887. 
"          Report  Board  of  Trustees,  University  of  Illinois,  1887-88. 
Kellerman  and  Swingle  :   First  Annual  Report,  Kansas  Experiment  Station,  i8£8. 


:    5  BULLETIN  xo.  6.  [August, 

crop.  The  season  (iSS~)  was  quite  dry,  and  there  was  at  no  time  subse- 
quent to  the  planting  any  superfluous  water  in  the  area  described.  The 
seed  germinated  and  the  young  corn  grew  satisfactorily  until  after  the 
second  plowing  when  the  plants  were  more  than  six  inches  high.  Then 
the  newly  tilled  spot  showed,  by  the  change  in  the  appearance  of  the  corn, 
in  a  very  definite  manner,  to  the  very  furrow  on  the  margins,  a  distinct 
difference  from  the  rest  of  the  field.  The  corn  ceased  growing,  became 
yellow  and  unusually  slender,  then  for  the  most  part  died.  Careful  exam- 
inations showed  that  the  trouble  was  not  due  to  insects,  but  to  the  im- 
mediate agency  of  the  bacteria  described  below.  The  destruction  was  so 
complete  that  the  spot  was  replanted,  and,  singularly  enough,  this  time 
grew  to  large  size  though  more  or  less  diseased-  A  few  stalks  of  the  first 
planting  after  a  time  seemed  to  recover  from  the  malady  and  for  a  long 
time  showed  high  above  the  younger  growth.  But  ordinarily  there  are  no 
such  definite  borders  to  the  infected  areas,  and  often  nothing  whatever  to 
suggest  a  reason  for  their  peculiar  distribution.  It  may  be  stated  here 
that  later  in  the  season,  after  the  tassels  have  appeared,  the  disease  may 
be  found  widely  scattered  throughout  the  field,  affecting  only  here  and 
there  a  stalk  or  hill,  while  the  rest  remains  free  from  it. 

Upon  closer  observation  it  is  found  that  young  diseased  plants, 
besides  being  smaller  than  the  healthy  ones,  are  uniformly  yellowish  in 
color,  the  lowest  leaves  showing  worst  As  death  overtakes  these  leaves, 
they  apparently  succumb  by  a  general  decline  from  the  healthy  state,  and 
rarely  die  and  wither  chiefly  at  the  ends  and  margins  as  in  some  other 
cases.  When  some  of  the  affected  plants  are  pulled  from  the  ground, 
they  are  found  to  give  way  too  easily  in  consequence  of  the  death,  to  a 
greater  or  less  extent,  of  the  oldest  and  lowest  roots.  In  anything  like 
severe  cases  at  least  one-half  the  roots — always  the  lowest — are  injured 
and  usually  dead.  The  bottom  portion  of  the  stalk  is  likewise  affected 
and  will  be  found  dead  or  dying.  If  split  longitudinally  through  the 
middle,  the  inner  tissue  of  this  lower  part  is  seen  to  have  a  uniform  dark 
color;  and  a  similar  discoloration,  gradually  becoming  less  and  less  pro- 
nounced, appears  in  the  next  succeeding  nodes  or  joints,  while  the  spaces 
between  them  (internodes)  are  seemingly  healthy.  On  the  surface  when 
carefully  freed  from  dirt,  brownish,  corroded  spots  can  be  found,  some- 
times strictly  bordered,  again  diffusely  spreading.  Sometimes  masses  of 
semi-transparent,  rather  firm,  gelatinous  material  are  found  upon  these 
external  corrosions. 

After  midsummer,  especially,  the  disease  becomes  apparent  through 
discolorations  of  the  portions  of  the  leaves  called  the  sheaths,  which 
closely  invest  the  stalk.  These  leaf-sheaths  become  variously  spotted  as 
observed  from  the  exterior.  Sometimes  the  watery-brown  portions  are 
mere  specks:  sometimes  large  irregular  patches,  and  of  all  grades  between 
these  extremes.  The  discolorations  become  brown,  of  a  half-rotten  appear- 
ance. Occasionally  there  is  a  little  reddish  color,  more  often  bordering 
the  brown.  If  now  these  affected  leaves  are  stripped  from  the  stalk,  it 


1889]  A    BACTERIAL    DISEASE    OF    CORN.  169 

will  be  found  that  the  evidence  of  injury  is  much  more  conspicuous  on 
their  inner  side.  The  injured  patches  are  larger,  have  a  more  watery 
appearance  and  sometimes  are  more  or  less  smeared  with  the  same  gelat- 
inous substance  previously  mentioned  as  occurring  on  the  diseased  stem 
below  ground;  but  here  on  the  leaf-sheaths  it  is  usually  spread  in  a  thin- 
ner coating  or  layer,  instead  of  in  rounded  masses.  This  infection  of  the 
leaf-sheaths  evidently  comes  later  in  the  season  than  the  first  noticed 
form  of  the  disease  on  the  roots.  It  seems  also  to  be  evenly  distributed 
through  the  field  and  to  occur  upon  large  as  well  as  small  plants. 

Finally,  the  ears  are,  at  least  occasionally,  affected.  Externally,  the 
appearance  of  the  outer  husks  is  like  that  of  the  diseased  leaf-sheaths. 
Internally,  in  the  worst  stage,  the  whole  ear — husks,  which  should  be  still 
green,  young  cob  and  kernels,  and  the  mass  of  "  silks  " — is  reduced  to  a 
moist  state  of  corruption,  though  not  ill-scented.  The  parts  lose  their 
normal  rigid  or  turgid  quality,  appear  as  if  wilted,  and  are  packed  closely 
together,  if  not  actually  adhering  by  the  gummy  exudation  from  the 
tissues.  Very  often  these  ears  subsequently  become  mouldy,  penetrated 
through  and  through  by  a  close,  very  white,  felt-like  fungus.  Possibiy 
this  fungus  sometimes  makes  its  inroads  into  the  ear  without  the  bacteria 
as  forerunners:  but  from  present  knowledge  it  seems  probable  that  it  is  a 
secondary  intruder.  These  mouldy  ears  are  in  certain  seasons  very 
numerous  and  are  readily  recognized  by  the  busker,  as  well  as  by  the 
buyer  when  the  loads  are  sent  to  market. 

HISTORY  OF  INVESTIGATION*. 

During  the  year  1882,  Professor  S.  A.  Forbes,  while  studying  the  work 
of  chinch  bugs  on  corn,  sent  me  for  examination  portions  of  corn  stalks 
and  leaves,  collected  in  McLean  county,  upon  which  were  found  the  cor- 
roded spots  above  described,  and,  associated  with  these,  the  gelatinous 
substance  above  referred  to.  During  this  same  time  the  chinch  bugs 
were  found  to  be  infested  with  bacteria,  which  soon  swept  them  all  off  by 
a  veritable  contagion.  Since  the  bacteria- possessed  insects  were  found 
on  the  corn  and  these  lumps  of  jelly  also  full  of  bacteria  along  with  them 
on  the  corroded  leaf-sheaths  (the  injury  was  then  supposed  to  be  solely 
the  work  of  the  insects),  notwithstanding  tne  different  appearance  of  the 
organisms  under  the  microscope,  the  jelly  was  referred  to  in  the  published 
description  of  the  chinch  bug  parasite*  as  zooglara  masses.  '  The  state- 
ment was,  however,  shown  to  be  doubtful  by  the  insertion  of  an  interro- 
gation mark. 

This  is  believed  to  be  the  first  published  reference — slight  as  this  is — 
to  the  cotn  parasite  with  which  we  now  deal. 

At  various  times  many  examinations  were  made  upon  the  roots  of 
sickly  corn  in  which  there  was  no  evidence  of  insect  work,  with  the  ex- 
pectation of  finding,  if  anything,  the  mycelium  of  a  fungus.  These  once 


•American  Naturalist.  1883.  p.  319. 


170  BULLETIN    NO.    6.  [August, 

and  again  proved  abortive,  and  the  conclusion  was  finally  reached  that  no 
such  parasitic  growth  existed  in  connection  with  the  malady. 

The  next  critical  investigation  of  growing  corn  affected  with  the  dis- 
ease came  about  in  a  very  similar  manner.  During  several  years  preced- 
ing 1889,  the  chinch  bugs  were  exceedingly  numerous  and  destructive, 
especially  throughout  the  southern  portion  of  Illinois,  and  the  state  entomol- 
ogist was  earnestly  endeavoring  to  collect  all  possible  information  concern- 
ing them  and  the  peculiarities  of  their  life  history.  At  Albion,  Edwards 
county,  111.,  a  field  of  corn  belonging  to  J.  Skeavington  was  found  which 
presented  so  poor  an  appearance,  without  evidence  of  insect  depredations, 
that  in  July,  1887,  Professor  Forbes  brought  home  some  of  the  plants  for 
further  study.  Some  of  these  were  turned  over  to  me  for  examination. 
The  descriptions  already  given  of  the  affected  roots  and  leaf-sheaths 
might  have  been  written  from  these  stalks;  and,  furthermore,  the  organ- 
ism was  identified  to  which  we  now  attribute  the  malady.  Search  was 
now  made  in  fields  near  the  University  and  the  disease  was  found  in 
progress.  Studies  were  carried  on  during  some  weeks,  the  specific  organ- 
ism being  invariably  found  associated  with  the  affected  parts;  pure 
cultures  were  secured  and  inoculations  made  in  healthy  corn.  The  latter 
failed.  On  this  account  no  publication  was  made  of  the  facts  obtained, 
it  being  thought  desirable  to  ascertain  positively  the  causative  action  of 
the  bacteria  before  proceeding  further.  During  the  season  of  1888, 
other  things  demanding  first  attention,  no  further  studies  were  made  upon 
the  disease  except  to  note  its  occurrence  and  distribution.  A  field  of 
forty  acres  near  Kankakee,  Illinois,  was  found  almost  ruined  by  this  dis- 
ease. In  this  case  the  land  was  excellent  in  quality  and  in  good  condition, 
and  the  corn  had  been  well  cultivated.  The  seed  had  come  up  well,  and 
for  a  time  the  growth  progressed  finely;  but  nearly  all  the  stalks  remained 
abnormally  small;  many  gave  no  indications  of  earing  and  the  best  of 
them  produced  "nubbins"  rather  than  ears.  It  was  found  here,  as  in 
some  previous  cases,  that  after  the  lowest  roots  had  died  and  others  had 
been  put  forth  above  the  former,  these  later  roots  soon  became  diseased. 
Sometimes  when  the  "brace"  roots  issuing  from  the  stem  above  ground 
reached  and  penetrated  the  soil,  they,  too,  became  corroded,  or  sloughed 
off  in  a  mass  of  brown  mucilage,  thus  in  effect  destroying  the  plant.  The 
characteristic  bacteria  were  found  present. 

The  next  thing  which  drew  renewed  attention  to  the  matter  was  the 
discovery  by  Dr.  F.  S.  Billings,*  of  the  Agricultural  Experiment  Station 
of  the  University  of  Nebraska,  an  acute  observer  and  thorough-going 
pathologist,  of  a  "germ  "  in  cattle  which  had  died  after  feeding  upon  corn 
stalks  in  the  field,  at  Ames,  Nebraska,  January  6,  1888.  Other  cases 
occurred  at  different  places  in  the  state  and  received  more  or  fess  atten- 
tion until,  finally,  in  the  winter  and  spring  of  1889,  the  distinguished 
investigator  took  up  the  subject  for  more  special  research.  Having 


*  Original  Investigations  of  Cattle  Diseases  in  Nebraska,   1886-88,  Bulletin  of   Experiment  Station  of 
Nebraska. 


1889]  A    BACTERIAL    DISEASE    OF    CORN.  171 

learned  of  my  examinations  of  corn  diseased  in  the  fields,  he  asked  me 
for  a  description  which  he  included  (page  199)  in  the  volume  referred  to. 
He  also  sent  cultures  of  the  organisms  obtained  by  him  from  infected 
animals  for  comparison  with  those  taken  by  me  from  the  growing  corn. 
They  seemed  to  be  alike.  In  March  I  applied  the  Billings  "germ"  from 
a  culture  to  some  young  corn  which  we  happened  to  have  growing  in  the 
greenhouse.  Nothing  came  of  this,  though  inoculations  and  smearings 
were  made  in  several  ways.  Rabbits  and  mice,  however,  quickly  suc- 
cumbed upon  inoculation.  Some  wild  gray  rabbits,  which  had  been 
proof  against  the  hog  cholera  "germ,"  died  within  six  days  after  sub- 
cutaneous inoculation. 

Finally  Professor  Forbes  found,  near  Sycamore,  Illinois,  July,  1889, 
indications  of  this  newly  studied  disease  throughout  considerable  areas. 
He  again  brought  in  specimens  and  examination  proved  his  suspicion 
correct.  Soon  afterward  the  writer  visited  the  fields  mentioned  and  many 
others  through  the  northern  part  of  the  state.  Of  the  places  visited  the 
disease  seemed  to  be  worst  in  the  Sycamore  region;  but  more  or  less  evi- 
dence of  it  was  found  in  numerous  widely  separated  localities.  At  Syca- 
more some  improvement  had  apparently  taken  place  since  the  first  named 
observation,  the  later  roots  appearing  free  from  injury.  But  in  certain 
fields  a  large  percentage  of  the  stalks  showed  no  indications  of  earing  and 
could  not,  it  was  thought,  after  that  time  (August  ist),  produce  anything 
like  a  satisfactory  crop. 

After  receiving  the  first  diseased  plants  from  Sycamore,  search  was 
again  made  at  Champaign,  and  the  malady  was  found  in  several  fields. 
Cultures  and  inoculations  upon  growing  corn  were  made,  and  this  time 
with  unmistakable  results.  The  bacteria,  in  pure  cultures,  were  applied  to 
the  inner  surface  of  the  leaf-sheaths,  without  puncture,  and  the  watery- 
brown  spots  appeared  in  four  days  while  the  organisms  multiplied  enor- 
mously in  numbers  and  were  taken  still  pure — in  favorable  cases — in 
considerable  quantity  from  the  affected  surfaces. 

Time  has  not  permitted  a  large  number  of  these  experiments,  and  the 
results  so  far  obtained  do  not  warrant  a  conclusion  as  to  the  reason  of 
previous  failures  in  the  greenhouse  and  out  of  it;  neither  have  we,  so  far, 
satisfactory  results  from  application  to  the  roots  and  subterranean  stems. 
But  with  the  positive  results  from  inoculation  of  the  leaf-sheaths  and  the 
abundant  evidence  upon  examination  and  culture,  it  cannot  be  doubted 
that  the  specific  bacteria  are  the  direct  agents  in  the  destructive  work. 

This  is  written  August  i6th.  During  the  last  ten  days  inoculation 
and  feeding  experiments  upon  a  small  scale  have  been  tried  upon  rabbits 
without  positive  results.  These  tests  are  too  few  and  too  recent  to  be  of 
much  import  'here;  but  they  do  serve  to  show  that  the  "germ,"  if  the 
same  as  that  in  the  experiments  of  Dr.  Billings,  has  not  now  the  virulence 
that  his  had  either  with  him  or  myself.  The  identity  of  the  two  is  there- 
fore still  to  be  proved. 


172  BULLETIN   NO.    6.  \_AugUSt, 

THE  BACTERIA. 

As  has  been  indicated  above,  the  disease  organisms  in  this  case  are 
found  in  great  numbers  on  and  within  the  affected  parts  of  the  roots,  the 
subterranean  stem,  the  leaf,  and  the  ear.  In  many  cases  they  collect  on 
these  surfaces  in  gelatinous  lumps  or  masses  which  really  consist,  for  the 
most  part,  of  the  organisms  themselves  held  together  by  the  stiff  muci- 
laginous substance  which  they  themselves  exude.  If.  a  microscopical 
preparation  is  made  directly  from  this  jelly,  it  will  be  found  that  the  indi- 
vidual organisms  are  quite  variable  in  shape,  though  many  of  them  are 
elongated,  almost  cylindrical,  with  somewhat  tapering  ends.  The 
usual  stains  affect  these  little  rods  in  a  peculiar  manner.  One,  or  more, 
often  two,  dot-like  portions  take  a  deep  color  while  the  rest  remains 
unstained.  When  these  dots  are  near  the  middle,  as  is  more  often  the 
case,  the  extremities  usually  become  less  and  less  visible,  until  it  is  only 
possible  to  make  out  the  terminal  portions  with  a  good  objective  and 
excellent  illumination.  But  mixed  with  these  elongated  forms  are  many 
of  quite  uniformly  oval  shape,  very  often  joined  two  and  two  by  their 
contiguous  ends.  These  stain  solid  throughout,  or  are  paler  in  a  central 
transverse  band.  All  variations  occur  from  a  very  narrow  pale  central 
band  up  to  a  very  wide  one,  and  in  the  latter  case  only  the  tips  of  the  ovals 
are  colored  by  the  dye.  These  peculiarities  of  staining  are  almost 
exclusively  confined  to  the  fresh  substance  as  collected  from  the  plants. 
When  the  bacteria  have  been  grown  in  artificial  cultures,  they  usually 
stain  uniformly  solid  throughout,  though  occasionally  pale-centered  indi- 
vidvals  are  found.  Upon  first  examination,  any  observer  would  at  least 
suspect  that  the  oval  and  elongated  forms  described  were  different  spe- 
cies; but  cultivation  tests  show  that  both  belong  to  one  and  the  same 
thing,  and  in  all  artificial  media  tried  they  are  always  quite  or  nearly  oval 
in  shape,  though  often  differing  considerably  in  size  after  the  culture 
becomes  more  than  eighteen  to  twenty  hours  old. 

They  divide  in  one  plane  only,  in  the  direction  of  the  short  axis.  It 
is  very  common,  especially  when  they  are  rapidly  growing,  to  find  them 
in  couples;  but  they  rarely  adhere  in  strings  of  greater  numbers.  They 
multiply  rapidly  at  the  ordinary  temperature  of  the  laboratory,  but  seem 
to  grow  fastest  at  about  36°  C.  (97°  F.).  It  should  be  said,  however, 
that,  though  the  recent  work  was  done  in  midsummer,  the  room — in  the 
basement  of  a  large  building  and  on  the  north  side — was  always  cool 
enough  for  comfort. 

In  notes  made  upon  the  organisms  in  1887,  they  were  said  to  have 
swimming  movements  in  fluids;  but  in  the  examinations  made  in  1889,  such 
movements  have  not  been  detected,  though  trials  were  made  from  fresh 
liquid  and  solid  cultures,  in  beef  broth  and  in  water,  at  the  ordinary  temper- 
ature of  the  room  and  warmed  upon  the  stage  to  36  °  or  37  °  C.  However, 
these  trials  were  only  made  a  few  days  before  this  writing  and  may  not 
indicate  the  full  truth.  This  peculiarity  of  movement  differs  greatly 
according  to  conditions,  though  certain  species  never  possess  it. 


1889]  A    BACTERIAL    DISEASE    OF    CORN.  173 

Nutrient  gelatine  is  not  liquified.  In  a  "  stab  "  culture  in  this  medium 
there  is  to  be  seen  along  the  needle  tract  after  twenty-four  hours,  a  gray- 
ish streak,  which  becomes  slightly  diffused  by  minute  lateral  ramifications 
into  the  substance,  the  borders  not  being  very  definitely  marked.  But 
the  spreading  does  not,  with  more  time,  long  continue;  hence  the  line 
does  not  become  more  than  an  eighth  of  an  inch  wide.  On  the  surface 
the  growth  spreads  in  a  definitely  bordered  circle,  commonly  somewhat 
wavy,  and  is  lusterless.  On  the  sloping  surface  of  an  agar  tube  the  growth 
is  prompt  and  characteristic,  forming  during  twenty  to  thirty  hours  at 
36°  C.  an  opaque,  lusterless,  white  streak  with  margins  nearly  even  or  reg- 
ular. On  examination  with  a  lens,  it  can  be  made  out  that  the  mass  is 
not  entirely  homogenous.  There  are  obscure  rays  of  more  or  less  opaque 
character,  sometimes  giving  a  slightly  feathered,  often  a  simply  mottled, 
appearance.  If  the  medium  is  quite  moist,  the  pasty  mass  at  length  runs 
down  and  collects  at  the  bottom  of  the  tube.  The  growth  never  becomes 
diffused  in  a  film  over  the  surface.  In  liquids  the  tube  becomes  uniformly 
turbid  within  twenty-four  hours,  plainly  more  so  in  the  incubator  at  the 
temperature  named.  At  the  end  of  this  time,  though  not  much  before, 
there  appears  on  the  surface  a  thin,  fragile  pellicle  which  readily  breaks 
up  on  handling  and  slowly  settles  to  the  bottom.  No  spores  are  formed. 

In  fresh  cultures  of  beef  broth  the  ovals  average  a  little  longer  than 
they  do  when  grown  on  solid  media.  On  quite  moist  agar,  the  two  diam- 
eters of  the  individuals  in  a  culture  eighteen  hours  old  differ  but  slightly 
and  the  shape  is  very  uniform.  The  transverse  measure,  however,  in  all 
fresh  cultures  is  very  nearly  uniform  and  is  about  .65  micron  (.00026  in.). 
The  most  common  length  of  a  newly  divided  pair  is  1.6  micra;  each 
individual  being  about  .8  micron.*  Single  ones  average  a  little  longer  and 
occasionally  reach  the  length  given  for  a  pair. 


*A  micron  is  one-thousanth  of  a  millimeter,  or  about  one  twenty-five-thousanth  of  an  inch. 


174 


BULLETIN    NO.    6. 


FIGURE  SHOWING  FORMS  OF  THE  BACTERIA,  MULTIPLIED  3,333  TIMES. 


•* 

«   /N   »     ii     '- 


Desciiplion  of  Figure.  —  The  figure  is  a  photo  engraving  from  a  drawing  by  A.  M. 
Wesiergren,  under  a  Tolles'  ^g-inch  homogenous  immersion  objective,  with  aHughenian 
eye  piece  furnished  with  a  Rogers  micrometer.  The  instrument  magnified,  as  used,  1,650 
times  (diameters).  Lines  were  drawn  on  the  paper  corresponding  to  those  of  the  mi- 
crometer, so  as  to  mate  the  magnification  exactly  5,000  times.  Reduction  of  one-tlvrd 
was  made  in  the  engraving,  so  that  the  representation,  as  it  now  appears,  is  3,333  times 
the  natural  size.  In  making  the  drawing  there  were  used  three  slides  from  cultures  each 
of  which  was  known  to  be  pure,  and  one  slide  made  directly  from  the  gelatinous 
substance  on  a  leaf-sheath.  The  endeavor  was  made  to  select  from  these  four  slides  all 
forms  and  sizes  of  the  organisms  which  they  contained  and  thus  to  show,  as  nearly  as 
possible,  all  the  variations  of  the  species.  Every  individual  figured  was  drawn  as  accu- 
rately as  possible  from  the  actual  object.  Methyl-violet  stain  was  used. 

The  typical  form  is  represented  by  those  of  medium  size  having  an  oval  shape, 
most  numerously  shown.  The  largest  ones  are  indicated  by  the  two  near  the  center  of 
the  figure,  and  the  peculiar  appearance  of  those  not  becoming  uniformly  stained  is  shown 
near  the  top.  The  two,  near  together,  with  dark  color  near  the  ends  only  and  a  much 
paler  but  somewhat  colored  central  area,  are  types  of  those  obtained  from  mounts  made 
directly  from  the  diseased  plants.  The  seemingly  perfectly  spherical  forms  are  supposed 
to  he  standing  on  end,  though  there  is  some  doubt  in  regard  to  the  largest  of  these.  The 
greatly  elongated  forms  with  central  dots  are  not  shown  in  the  figure. 


REMEDIAL  TREATMENT. 

We  know  too  little  of  the  disease  to  be  able  to  suggest  a  remedy.  In 
the  studies  made  during  the  last  two  weeks  especially,  there  appears  to  be 
in  a  considerable  number  of  cases  more  injury  on  land  which  has  been 
planted  with  corn  the  preceding  year,  though  the  rule  does  not  always 
hold  good.  In  one  case  the  worst  results  followed  when  timothy  sod  had 


1879]  A    RACTER1AL    DISEASE    OF    CORN.  175 

been  broken  up  and  corn  planted  thereon;  while  a  timothy  pasture  not  far 
distant,  treated  in  the  same  manner  gave  a  thoroughly  healthy  crop  of 
corn.  Grass  and  weeds  have  been  'carefully  examined  without  finding 
indications  that  the  same  disease  affects  them.  Probably  the  bacteria 
live  over  winter  in  the  soil,  though  we  have  no  experimental  data  for  this 
opinion.  If  this  is  a  fact,  then  young  corn  would  be  liable  to  suffer  when 
growing  upon  land  on  which  the  preceeding  crop  was  diseased.  When  it 
is  definitely  known  whether  anything  besides  corn  is  affected,  we  shall  be 
better  able  at  least  to  theorize  upon  a  cure. 

From  observations  now  made  it  appears  that  the  disease  is  a  very 
prevalent  one  and,  probably,  has  existed  during  the  time  that  corn  has 
been  grown  on  the  continent.  If  so,  it  has  not  ordinarily  attracted  atten- 
tion and,  very  likely,  is  not  destructive  enough  to  be  specially  noticed. 
When,  however,  under  peculiar  circumstances,  the  crop  is  injured  to  the 
extent  now  sometimes  known,  the  loss  is  very  great,  not  only  to  individual 
farmers,  but  to  the  country  at  large. 

THOMAS  J.  BURRILL,  Ph.  D., 

Horticulturist  and  Botanist. 


All  communications  intended  for  the  Station  should  be  addressed, 
not  to  any  person,  but  to  the 

AGRICULTURAL  EXPERIMENT  STATION,  CHAMPAIGN,  ILLINOIS. 

The  bulletins  of  the   Experiment  Station  will  be  sent  free  of  all 
charges  to  persons  engaged  in  farming  who  may  request  that  they  be  sent. 

SELIM  H.  PEABODY, 

President  Board  of  Direction. 


BULLETIN    NO.    6.  [August,   1889. 


ORGANIZATION. 


BOARD  OF  TRUSTEES  OF  THE  UNIVERSITY  OF  ILLINOIS. 

ALEXANDER  McLEAN,  Macomb,  President. 

JOSEPH  W.  FIFER.  Governor  of  Illinois. 
GEORGE  S.  HASKELL,  Rockford,  President  State  Board  of  Agriculture. 

RICHARD  EDWARDS,  Superintendent  of  Public  Instruction, 

S.  M.  MILLARD,  Highland  Park.  GEORGE  R.  SHAWHAN,  Urbana. 

CHARLES  BENNETT,  Mattoon.  W.  W.  CLEMENS,  Marion. 

OLIVER  A.  HARKER,  Carbondale.  FRANCIS  M.  McKAY,  Chicago, 

EMORY  COBB,  Kankakee.  SAMUEL  A.  BULLARD,  Springfield. 


BOARD  OF  DIRECTION  OF  THE  EXPERIMENT  STATION. 

SELIM  H.  PEABODY,  LL.  D.,  Champaign,  Regent  of  the  University,  President. 

E.   E.   CHESTER,  Champaign,  of  State  Board  of  Agriculture. 

HENRY  M.  DUNLAP,  Savoy,  of  State  Horticultural  Society. 

H.  B.  CURLER,  DeKalb,  of  State  Dairymen's  Association. 

EMORY  COBB,  Kankakee,  Trustee  of  the  University. 

CHARLES  BENNETT,  Mattoon,  Trustee  of  the  University. 

GEORGE  S.  HASKELL,  Rockford,  Trustee  of  the  University.    ' 

GEORGE  E.  MORROW,  A.  M,  Champaign,  Professor  of  Agriculture. 

THOMAS  J.   BURR1LL,  Ph.  D.,  Urbana,  Professor  of  Botany  and  Horticulture. 


THE  STATION  STAFF. 

GEORGE  E.  MORROW,  A.  M.,  Agriculturist. 
THOMAS  J.  BURRILL,  Ph.  D.,  Horticulturist  and  Botanist. 

DONALD  McINTOSH,  D.  V.  S.,  Veterinarian. 

THOMAS  F.  HUNT,  B.  S.,  Assistant  Agriculturist. 

GEORGE  W.  McCLUER,  B.  S.,  Assistant  Horticulturist. 

ALBERT  G.   MANNS,  Ph.  D.,  Assistant  Chemist. 

B.  S.,  Assistant  Chemist. 

WILLIAM  L.  PILLSBURY,  A.  M.,  Champaign,  Secretary. 


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